<!DOCTYPE html>
<html>

<head>
    <meta charset="utf-8">
    <title>菜鸟教程(runoob.com)</title>
</head>

<body>

    <p>点击下面的按钮，只要 i 小于 5 就一直循环代码块。</p>
    <button onclick="myFunction()">点击这里</button>
    <p id="demo"></p>
    <script>
        function myFunction() {
            var x = "", i = 0;
            do {
                x = x + "该数字为 " + i + "<br>";
                i++;
            }
            while (i < 5)
            document.getElementById("demo").innerHTML = x;
        }
    </script>

</body>

</html>